Preparation of selected epoxides

Abstract

A process for the production of epoxides of the formula (I): <IMAGE> (I) in which the benzene ring A is substituted with 1 to 3 halogen atoms, which are the same or different, and optionally carries other substituents, and R1 is <IMAGE> which is the same as or different from the other group <IMAGE> or C1-6 alkyl, the process comprising electrolyzing the corresponding alkene of the formula (II): <IMAGE> (II) in a medium comprising a solvent for the alkene and an aqueous solution of a halogen salt, the solvent/water ratio by weight being greater than unity, the solvent being miscible with water at the solvent/water ratio used and being chemically inert to both the alkene and the free halogen produced from the halogen salt by the electrolysis. The epoxides are useful in the synthesis of fungicidal compounds and certain of the epoxides are novel compounds.

What is claimed is: 
     
       1. A process for the production of epoxides of the formula (I): ##STR17## in which the benzene ring A is substituted with 1 to 3 halogen atoms, which are the same or different, and optionally carries other substituents, and R 1  is ##STR18## which is the same as or different from the other group ##STR19## or C 1-6  alkyl, the process comprising electrolysing the corresponding alkene of the formula (II): ##STR20## in a medium comprising a solvent for the alkene and an aqueous solution of a halogen salt, the solvent/water ratio by weight being greater than unity, the solvent being miscible with water at the solvent/water ratio used and being chemically inert to both the alkene and the free halogen produced from the halogen salt by the electrolysis. 
     
     
       2. A process according to claim 1 in which the water content of the medium is from 3 to 25% by volume of the total medium. 
     
     
       3. A process according to claim 1 in which the water content of the medium is from 5 to 10% by volume of the total medium. 
     
     
       4. A process according to claim 1 in which there is present in the medium at least 1 mol of water per mol of alkene. 
     
     
       5. A process according to claim 1 in which the solvent has a dielectric constant greater than 30. 
     
     
       6. A process according to claim 1 in which the solvent is selected from dimethyl formamide, acetonitrile, sulpholane, N-methyl pyrrolidone, dimethyl acetamide and dimethyl sulphoxide. 
     
     
       7. A process according to claim 1 in which the initial pH of the medium is greater than 7. 
     
     
       8. A process according to claim 1 in which at least half of the cations other than hydronium ions present in the medium are ammonium, substituted ammonium or a mixture thereof. 
     
     
       9. A process according to claim 1 in which the halogen salt is a bromide. 
     
     
       10. A process according to claim 1 in which the halide concentration is in the molar range 0.1 to 0.2M.